Polyamide elastomer, medical device, and method for producing polyamide elastomer

ABSTRACT

A polyamide elastomer comprising a reaction product of components (a), (b), and (c). Component (a) has the formula HOOC—R1—(—NH—CO—R1-)n—NH2 (where each R1 independently is linear saturated hydrocarbon, n represents a real number of 0 or greater, and when the formula contains multiple repeating units each containing R1, n represents a total number of those repeating units) and the Mn of component (a)=4000-10000. Component (b) has the formula HOOC—R2—COOH (where R2 represents a direct bond or a linear saturated hydrocarbon group). Component (c) has the formula H2N—R4—(—O—R4-)m—NH2 (where each R4 independently represents a saturated hydrocarbon group containing 1 or more carbon atoms; m represents a real number of 1 or more; and when the formula contains two or more types of the repeating units each containing R4, m represents a total number of the two or more types of the repeating units each containing R4).

TECHNICAL FIELD

The present invention relates to a polyamide elastomer, a medical devicehaving the polyamide elastomer, and a method of producing the polyamideelastomer.

BACKGROUND ART

Polyamide elastomers are a resin compound that is widely used in variousfields, such as packaging materials for food and the like; medicaldevice members; members of electrical devices, machines, and precisioninstruments; and automobile members. The medical device members that aremade of a polyamide elastomer include medical tubes and catheterballoons. For use in production of such medical device members, apolyamide elastomer is required to have moldability, such as extrusionmoldability and blow moldability, which is the ability of the polyamideelastomer to be formed precisely into a desired shape, and dynamicalproperties, such as elasticity, elongation at break, and strength atbreak, which are the ability of the polyamide elastomer to withstandpotential destruction caused by pressure or bending force applied duringuse.

Patent Literature 1 discloses a block polyether amide that is obtainedby condensation polymerization of a certain polyamide having a carboxygroup on either end, a polyoxyalkylene having an amino group on eitherend and having an alkylene group containing 3 or more carbon atoms, anda certain diamine. Patent Literature 2 discloses a polyether amide thatis obtained by polycondensation of a polyamide-forming monomer, apolyoxyalkylene having an amino group on either end and having analkylene group containing 3 or more carbon atoms, a certain diamine, anda certain amount of dicarboxylic acid. The polyether amides of PatentLiteratures 1 and 2 are likely to have a certain degree of elasticityand impact resistance. However, in the polyether amides with thecompositions described in Patent Literatures 1 and 2, use of thepolyether having an alkylene group containing 3 or more carbon atoms isnot enough to attain sufficient mechanical strength, such as elasticity,elongation at break, and strength at break. Therefore, furtherimprovement has been demanded.

Patent Literature 3 discloses a polyamide elastomer that is obtained bypolymerization of (A) a polyamide-forming monomer selected from certainaminocarboxylic acid compounds and certain lactam compounds, (B) atleast one diamine compound selected from polyether diamines having apolytetramethylene oxide (PTMO) skeleton, branched diamines, branchedalicyclic diamines, and norbornane diamines, and (C) a certaindicarboxylic acid compound. All of the diamine compounds used in theinvention described in Patent Literature 3, however, have poorreactivity and thereby take a long time for polymerization. This maycause partial thermal cracking of the polymerization product duringpolymerization. This induces coloration of the resulting elastomer andcauses insufficient progression of the reaction of the diaminecompounds, impairing the strength characteristics of the resultingelastomer, such as elongation at break and strength at break.

Patent Literature 4 discloses a polyether-polyamide copolymer resin thathas an elongation at break of 1000% or higher and a modulus ofelasticity of 15 MPa or lower and is for use in coating of orimpregnation into flexible fabric. This patent literature discloses aspecific embodiment, which is a polyether polyamide resin obtainable bybinding a soft segment and a hard segment together. The soft segmentconsists of a polyether polyamide that is composed of a polyetherdiamine compound having a C₂₋₃ alkylene group and a certain dicarboxylicacid compound. The hard segment consists of a polyamide that is composedof a certain aminocarboxylic acid and/or a certain lactam compound.Here, the polyether component of the polyether polyamide resin describedin Patent Literature 4 has poor reactivity, so that the resin strengthat break is insufficient.

CITATIONS LIST Patent Literatures

Patent Literature 1: JP S59-193923 A

Patent Literature 2: JP S59-131628 A

Patent Literature 3: WO 2007/145324 A1

Patent Literature 4: WO 2009/139087 A1

SUMMARY OF INVENTION Technical Problems

In view of the above problems, an object of the present invention is toprovide a polyamide elastomer that is excellent in mechanical strengthproperties in a solid state, such as elasticity, elongation at break,and strength at break; excellent in extrusion moldability in a moltenstate; and excellent in moldability in a solid state, such as blowmoldability.

Solutions to Problems

The inventor of the present invention has conducted intensive researchto achieve the object described above, and thus completed the presentinvention. The present invention relates to a polyamide elastomeraccording to any one of [1] to [6] below, a medical device according toany one of [7] and [8] below, and a production method according to anyone of [9] to [11] below.

[1] A polyamide elastomer is a reaction product of at least components(a), (b), and (c), the component (a) having a number average molecularweight of 4000 or higher and 10000 or lower.

The component (a) is at least one compound represented by formula (1):[Formula 1]HOOC—R₁

NH—CO—R₁

_(n)NH₂  (1)

In the formula (1), each R₁ independently represents a linear saturatedhydrocarbon group containing 1 or more carbon atoms; n represents a realnumber of 0 or greater; and when the formula contains two or more typesof repeating units each containing R₁, n represents a total number ofthe two or more types of the repeating units each containing R₁.

The component (b) is at least one compound represented by formula (2).[Formula 2]HOOC—R₂—COOH  (2)

In the formula (2), R₂ represents a direct bond or a linear saturatedhydrocarbon group containing 1 or more carbon atoms.

The component (c) is at least one compound represented by formula (3):[Formula 3]H₂N—R₄

O—R₄

_(m)NH₂  (3)

In the formula (3), each R₄ independently represents a saturatedhydrocarbon group containing 1 or more carbon atoms; m represents a realnumber of 1 or greater; and when the formula contains two or more typesof repeating units each containing R₄, m represents a total number ofthe two or more types of the repeating units each containing R₄.

[2] The polyamide elastomer according to [1] is a reaction product of atleast the components (a) to (c) and a component (d). The component (d)is at least one compound represented by formula (4).[Formula 4]H₂N—R₃—NH₂  (4)

In the formula (4), R₃ represents a saturated hydrocarbon groupcontaining 1 or more carbon atoms.

[3] In the polyamide elastomer according to [1] or [2], wherein thecomponent (c) is a component (c1). The component (c1) is at least onecompound represented by formula (5)

In the formula (5), (x+z) represents a real number of 1 or greater and 6or smaller; and y represents a real number of 1 or greater and 20 orsmaller.

[4] In the polyamide elastomer according to any one of [1] to [3], thecomponent (d) is at least one aliphatic diamine selected fromethylenediamine, trimethylenediamine, tetramethylenediamine,hexamethylenediamine, undecamethylenediamine, dodecamethylenediamine,and 2,2-4/2,4,4-trimethylhexamethylenediamine.

[5] In the polyamide elastomer according to any one of [1] to [4], amolar ratio (AB) of amino groups in the component (a) (represented by(A)) to monocarboxyl groups in the component (b) (represented by (B)) issubstantially 1/1.

[6] The polyamide elastomer according to any one of [1] to [5] containsphosphorus compound in a manner of containing element phosphorus in anamount of 5 ppm or higher and 5000 ppm or lower.

[7] A medical device has a member that is made by using the polyamideelastomer as described in any one of [1] to [6].

[8] In the medical device according to [7], the member is a catheterballoon or a medical tube.

[9] A method of producing a polyamide elastomer as described in any oneof [1] to [6], the method includes:

step (i) of allowing the component (a) and the component (b) to react,thereby obtaining a prepolymer; and

step (ii) of mixing the prepolymer with the component (c) to react witheach other.

[10] In the method of producing a polyamide elastomer according to [9],the prepolymer is mixed with the component (c) and the component (d) toreact with each other.

[11] In the method of producing a polyamide elastomer according to [9]or [10], each of the components in at least the steps (i) and (ii) iscaused to react by a melt kneading method.

[12] The method of producing a polyamide elastomer according to any oneof [9] to [11], further includes adding a phosphorus compound in atleast one of the steps (i) and (ii) in an amount of 10 ppm or higher and10000 ppm or lower relative to the total amount of the components (a) to(c) or the total amount of the components (a) to (d).

Advantageous Effects of Invention

The present invention makes it possible to obtain a polyamide elastomerthat is excellent in dynamical properties in a solid state, such aselasticity, elongation at break, and strength at break; excellent inextrusion moldability in a molten state; and excellent in moldability ina solid state, such as blow moldability.

DESCRIPTION OF EMBODIMENTS

Embodiments of a polyamide elastomer of the present invention aredescribed below. The scope of the present invention is not limited tothese embodiments.

The polyamide elastomer of the present invention is a reaction productof at least components (a), (b), and (c). In other words, the polyamideelastomer of the present invention has structures derived from at leastthe components (a), (b), and (c). The component (a) has a number averagemolecular weight of 4000 or higher and 10000 or lower. Accordingly, suchcertain components (a) to (c) are used and the certain range of thenumber average molecular weight of component (a) is achieved, in otherwords, the structure derived from such certain component (a) having anumber average molecular weight of 4000 or more and 10000 or lower andthe structures derived from such certain components (b) and (c) areused, thereby attaining the effects of the present invention. Thepolyamide elastomer of the present invention has a hard segment that isa polyamide structural unit derived from the component (a) and/or apolyamide structural unit derived from a reaction product of thecomponents (b) and (c); and a soft segment that is a polyetherstructural unit derived from the component (c). When the component (a)having a number average molecular weight within the certain range isbonded to the component (c) via the component (b) to form a structuralunit, the resulting polymerization reactivity may be excellent becauseof the suitable balance between the length of the hard segment and thelength of the soft segment, leading to further enhancement in elongationat break and strength at break of the resulting polyamide elastomer.

Next, the components (a) to (c) and the polyamide elastomer of thepresent invention will be described in more detail.

The component (a) used in the present invention is at least one compoundrepresented by formula (1).[Formula 6]HOOC—R₁

NH—CO—R₁

_(n)NH₂  (1)

In formula (1), each R₁ represents the same linear saturated hydrocarbongroup containing 1 or more carbon atoms or independently represents alinear saturated hydrocarbon group containing 1 or more carbon atoms; nrepresents a real number of 0 or greater; and when the formula containstwo or more types of repeating units each containing R₁, n representsthe total number of the two or more types of the repeating units eachcontaining R₁. From the viewpoints of polymerization reactivity anddynamical properties of the resulting polyamide elastomer, it ispreferable that n be 1 or greater and 100 or smaller, more preferably 10or greater and 80 or smaller, further preferably 18 or greater and 77 orsmaller. Here, n may be determined from a number average molecularweight that is obtained by gel permeation chromatography (GPC).

The R₁ in the component (a) is simply required to be a saturatedhydrocarbon group containing 1 or more carbon atoms. From the viewpointsof polymerization reactivity and dynamical properties of the resultingpolyamide elastomer, it is preferable that R₁ be a saturated hydrocarbongroup containing 6 or more and 18 or less carbon atoms. Preferableexamples of the component (a) include aminocarboxylic acids such as 1-to 6-aminohexanoic acids, 1- to 7-aminoheptanoic acids, 1- to8-aminooctanoic acids, 1- to 9-aminononanoic acids, 1- to10-aminodecanoic acids, 1- to 11-aminoundecanoic acids, 1- to12-aminododecanoic acids, 1- to 14-aminotetradecanoic acids, 1- to16-aminohexadecanoic acids, 1- to 17-aminoheptadecanoic acids, and 1- to18-aminooctadecanoic acids, and condensation products thereof. When thecomponent (a) is a condensation product of aminocarboxylic acid, thecondensation product may be either derived from one type ofaminocarboxylic acid or two or more types of aminocarboxylic acid.

The toughness of the resulting polyamide elastomer tends to be enhancedas the carbon chain of R₁ becomes longer, in particular.

The component (a) has a number average molecular weight of 4000 orhigher and 10000 or lower, preferably 5000 or higher and 7000 or lower,more preferably 5000 or higher and 6000 or lower.

With the number average molecular weight being within this range, themechanical properties of the resulting block copolymer are excellent.

The number average molecular weight of the component (a) may bedetermined by gel permeation chromatography (GPC), for example. It isknown that the number average molecular weight thus measured variesabout 10%. Therefore, when GPC is adopted to determine the numberaverage molecular weight in the present invention, the average value ofa plurality of measurements is used as the number average molecularweight. When multiple measurements cannot be carried out, it is checkedwhether there is an overlap between the above range and the numberaverage molecular weight obtained by a single measurement±about 10%.When these two ranges overlap each other, it is considered that theabove conditions of the number average molecular weight of the component(a) of the present invention are satisfied.

The component (b) used in the present invention is at least one compoundrepresented by formula (2).[Formula 7]HOOC—R₂—COOH  (2)

In formula (2), R₂ represents a direct bond or a linear saturatedhydrocarbon group containing 1 or more carbon atoms.

The linear saturated hydrocarbon group is not particularly limited aslong as it contains 1 or more carbon atoms. From the viewpoints ofpolymerization reactivity and dynamical properties of the resultingpolyamide elastomer, it is preferable that the linear saturatedhydrocarbon group contain 2 or more and 10 or less carbon atoms.

Specific examples of the compounds usable as the component (b) include,but not limited to, dicarboxylic acids such as oxalic acid, malonicacid, succinic acid, glutaric acid, adipic acid, pimelic acid, subericacid, azelaic acid, and sebacic acid. Only one type of the dicarboxylicacids may be used, or two or more types of the dicarboxylic acids may beused.

The component (c) used in the present invention is at least one compoundrepresented by formula (3).[Formula 8]H₂N—R₄

O—R₄

_(m)NH₂  (3)

In formula (3), each R₄ represents the same saturated hydrocarbon groupcontaining 1 or more carbon atoms or independently represents asaturated hydrocarbon group containing 1 or more carbon atoms; mrepresents a real number of 1 or greater; and when the formula containstwo or more types of repeating units each containing R₄, m representsthe total number of the two or more types of the repeating units eachcontaining R₄. In formula (5) below, for example, m=x+y+z.

The saturated hydrocarbon group is not particularly limited as long asit contains 1 or more carbon atoms. From the viewpoint of excellentelasticity, it is preferable that the saturated hydrocarbon groupcontain 1 or more and 10 or less carbon atoms, more preferably 2 or moreand 4 or less carbon atoms. The saturated hydrocarbon group may haveeither a linear structure or a branched structure.

From the viewpoint of excellent reactivity, it is preferable that thecomponent (c) of the present invention be a component (c1).

The component (c1) used in the present invention is at least onecompound represented by formula (5).

Regarding x, y, and z in formula (5), (x+z) represents a real number of1 or greater and 6 or smaller and y represents a real number of 1 orgreater and 20 or smaller. With these values being within these ranges,an excellent balance between polymerization reactivity and elasticitymay be attained. It is preferable that (x+z) be 1 or greater and 5 orsmaller, further preferably 1 or greater and 3.8 or smaller. It ispreferable that y be 1 or greater and 15 or smaller, more preferably 1or greater and 9.2 or smaller. Here, x, y, and z may be determined byGPC measurement as described, for example, in examples below.

The component (c1) may be, for example, a polyether diamine compoundthat is an amino-modified form of polyoxyethylene, 1,2-polyoxypropylene,1,3-polyoxypropylene, or a polyoxyalkylene that is a copolymer of these.More specifically, Jeffamine ED products manufactured by HuntsmanCorporation (U.S.) are preferable, for example. Among these products,Jeffamine ED600 and ED900 each have a value of (x+z) in formula (4) of 1or greater and 6 or smaller and a value of y in the same formula of 1 orgreater and 20 or smaller. More specifically, ED900 has a value of (x+z)of 1 or greater and 6 or smaller; ED600 has a value of (x+z) of 1 orgreater and 3.8 or smaller; ED900 has a value of y of 1 or greater and15 or smaller; and ED600 has a value of y of 1 or greater and 9.2 orsmaller. It is preferable that ED600 and ED900, each having a value of(x+z) and a value of y within the above ranges, have number averagemolecular weights ranging from 500 to 700 and from 800 to 1000,respectively. Each of these number average molecular weights is thenumerical value calculated from the proton ratio that is obtained bynuclear magnetic resonance using deuterated chloroform solvent.

Examples of more preferable embodiments of the polyamide elastomer thatis a reaction product of at least the components (a) to (c) describedabove, in other words, more preferable embodiments of the polyamideelastomer having the structures derived from at least the certaincomponents (a) to (c) include embodiments attributable to reaction ofthe components (a) to (c) of Nos. 1 to 16 shown in Table 1, in otherwords, include embodiments that have structures derived from variouscombinations of the components (a) to (c) of Nos. 1 to 16 shown in Table1.

TABLE 1 No. Component (a) Component (b) Component (c) 1 6-Aminohexanoicacid Succinic acid Polyether diamine (number of (number of carbon 3.8 ≥x + z ≥ 1, 9.2 ≥ y ≥ 1 carbon atoms: 6) atoms: 4) 700 ≥ Mn ≥ 500 2 (apolymer satisfying Polyether diamine 77 ≥ n ≥ 30) 6.2 ≥ x + z ≥ 1, 13 ≥y ≥ 1 1000 ≥ Mn ≥ 800 3 Adipic acid Polyether diamine (number of carbon3.8 ≥ x + z ≥ 1, 9.2 ≥ y ≥ 1 atoms: 6) 700 ≥ Mn ≥ 500 4 Polyetherdiamine 6.2 ≥ x + z ≥ 1, 13 ≥ y ≥ 1 1000 ≥ Mn ≥ 800 5 Sebacic acidPolyether diamine (number of carbon 3.8 ≥ x + z ≥ 1, 9.2 ≥ y ≥ 1 atoms:10) 700 ≥ Mn ≥ 500 6 Polyether diamine 6.2 ≥ x + z ≥ 1, 13 ≥ y ≥ 1 1000≥ Mn ≥ 800 7 Dodecanedioic acid Polyether diamine (number of carbon 3.8≥ x + z ≥ 1, 9.2 ≥ y ≥ 1 atoms: 12) 700 ≥ Mn ≥ 500 8 Polyether diamine6.2 ≥ x + z ≥ 1, 13 ≥ y ≥ 1 1000 ≥ Mn ≥ 800 9 12-AminododecanoicSuccinic acid Polyether diamine acid (number of carbon 3.8 ≥ x + z ≥ 1,9.2 ≥ y ≥ 1 (number of atoms: 4) 700 ≥ Mn ≥ 500 10 carbon atoms: 12)Polyether diamine (a polymer satisfying 6.2 ≥ x + z ≥ 1, 13 ≥ y ≥ 1 47 ≥n ≥ 18) 1000 ≥ Mn ≥ 800 11 Adipic acid Polyether diamine (number ofcarbon 3.8 ≥ x + z ≥ 1, 9.2 ≥ y ≥ 1 atoms: 6) 700 ≥ Mn ≥ 500 12Polyether diamine 6.2 ≥ x + z ≥ 1, 13 ≥ y ≥ 1 1000 ≥ Mn ≥ 800 13 Sebacicacid Polyether diamine (number of carbon 3.8 ≥ x + z ≥ 1, 9.2 ≥ y ≥ 1atoms: 10) 700 ≥ Mn ≥ 500 14 Polyether diamine 6.2 ≥ x + z ≥ 1, 13 ≥ y ≥1 1000 ≥ Mn ≥ 800 15 Dodecanedioic acid Polyether diamine (number ofcarbon 3.8 ≥ x + z ≥ 1, 9.2 ≥ y ≥ 1 atoms: 12) 700 ≥ Mn ≥ 500 16Polyether diamine 6.2 ≥ x + z ≥ 1, 13 ≥ y ≥ 1 1000 ≥ Mn ≥ 800

Since excellent mechanical strength of the resulting polyamide elastomeris obtained as long as the number average molecular weight of thecomponent (a) is within a predetermined range, not only the components(a) to (c) but also the component (d) may be subjected to reaction inthe present invention. More specifically, the polyamide elastomer of thepresent invention may be a reduction product of at least the components(a), (b), (c), and (d), in other words, the polyamide elastomer of thepresent invention may have structures derived from at least such certaincomponents (a) to (d).

The component (d) used in the present invention is at least one compoundrepresented by formula (4).[Formula 10]H₂N—R₃—NH₂  (4)

In formula (4), R₃ represents a saturated hydrocarbon group containingnot less than 1 carbon atom.

R₃ is not limited as long as it is a linear or branched saturatedhydrocarbon group containing 1 or more carbon atoms. From the viewpointof further enhancing the dynamical properties of the resulting polyamideelastomer, it is preferable that 2 or more and 14 or less carbon atomsbe contained, more preferably 4 or more and 12 or less carbon atoms becontained. Specific examples include, but not limited to, aliphaticdiamines such as ethylenediamine, trimethylenediamine,tetramethylenediamine, pentamethylenediamine, hexamethylenediamine,heptamethylenediamine, octamethylenediamine, nonamethylenediamine,decamethylenediamine, undecamethylenediamine, dodecamethylenediamine,2,2-4/2,4,4-trimethylhexamethylenediamine, and3-methylpentamethyldiamine. More preferable among these from the sameviewpoint as above is at least one aliphatic diamine selected fromhexamethylenediamine, heptamethylenediamine, octamethylenediamine,nonamethylenediamine, decamethylenediamine, undecamethylenediamine, anddodecamethylenediamine.

The molar ratio of the component (d), when used, to the component (c) inthe present invention is not particularly limited. From the viewpoint ofimparting excellent workability and excellent mechanical properties tothe resulting polyamide elastomer, it is preferable that the molar ratio(d/c) of the component (d) to the component (c) range from 8/2 to 1/9,more preferably from 7/3 to 2/8, further preferably from 6/4 to 3/7.This molar ratio may be determined from the amount of protons in theα-carbons adjacent to the terminal amine groups and the amount ofprotons in the α-carbons adjacent to the ether groups, all measured bynuclear magnetic resonance (NMR). During production, this molar ratiocorresponds to the molar ratio between the components used.

The molar ratio (AB) of amino groups in the component (a) (representedby (A)) to monocarboxyl groups in the component (b) (represented by (B))is not particularly limited in the present invention, but is preferably1/2 or higher and 5/4 or lower, more preferably and substantially be 1/1for easy obtainment of a polyamide elastomer with a preferable numberaverage molecular weight. The molar ratio being substantially 1/1 meansthat the number of moles of amino groups and the number of moles ofmonocarboxyl groups, which are calculated from the weight of the rawmaterial, are approximately the same with each other.

It is preferable that the polyamide elastomer of the present inventionhave a melt viscosity (melt flow rate, MFR) ranging from 0.1 to 20 g/10min at 230° C. and 2.16 kgf (21.2 N). With the melt viscosity beingwithin this range, excellent extrusion moldability is obtained. The meltviscosity within this range may be attained by appropriate adjustment ofthe polymerization reaction temperature, the reaction time, and theconcentration of the solution, for example.

It is preferable that the polyamide elastomer of the present inventionhave a Shore (D) hardness ranging from 50 to 100, more preferably from60 to 80. With the Shore (D) hardness being within this range, theresulting formed article has elasticity. The Shore (D) hardness withinthis range may be attained by appropriate adjustment of the amount ofthe component (c) to feed, or by appropriate adjustment of the ratio ofthe component (c) to the component (d) to feed when the component (d) isused.

It is preferable that the polyamide elastomer of the present inventionhave a number average molecular weight of 10000 or higher and not 150000or lower, more preferably 20000 or higher and 100000 or lower. With thenumber average molecular weight being within this range, excellentworkability and excellent mechanical properties are obtained.

It is preferable that a molded article made of the polyamide elastomerof the present invention have an elongation at break of 100% or higherand 600% or lower, more preferably 200% or higher and 600% or lower,measured in a tensile test; and a stress at break of 20 MPa or higherand 100 MPa or lower, more preferably 30 MPa or higher and 90 MPa orlower. The tensile test may be carried out by a method described below,for example.

The polyamide elastomer of the present invention may contain aphosphorus compound. With a phosphorus compound contained therein, theelongation at break and the stress at break of the resulting moldedarticle may be further enhanced and such a molded article is suitablefor use to make medical balloons, for example. In addition, potentialcoloration caused by stabilization of the polymerization reaction and byoxidation during production of the polyamide elastomer may be prevented,as described below. Examples of the phosphorus compound includephosphoric acid, pyrophosphoric acid, polyphosphoric acid, phosphorousacid, hypophosphorous acid, and alkali metal salts and alkaline-earthmetal salts thereof. Among them, phosphorous acid, hypophosphorous acid,and alkali metal salts and alkaline-earth metal salts thereof arepreferable from the viewpoints of enhancing polymerization reactionstability, imparting thermal stability to the resulting polyamideelastomer, and enhancing the dynamical properties of the resultingmolded article.

It is preferable that the content of the phosphorus compound be 5 ppm orhigher and 5000 ppm or lower, more preferably 20 ppm or higher and 4000ppm or lower, further preferably 30 ppm or higher and 3000 ppm or lowerin terms of the content of the element phosphorus.

In addition to the phosphorus compound, various additives may also becontained in the polyamide elastomer of the present invention forvarious purposes, as long as the properties of the polyamide elastomerof the present invention are not impaired. More specifically, aheat-resistant agent, an ultraviolet absorber, a light stabilizer, anantioxidant, an antistatic agent, a lubricant, a slip agent, anucleating agent, a tackifier, a mold release agent, a plasticizer, apigment, a dye, a flame retardant, a reinforcing agent, an inorganicfiller, a microfilament, and an x-ray opaque agent may be contained, forexample.

Next, embodiments of a method of producing a polyamide elastomer of thepresent invention will be described. The scope of the present inventionis not limited to these embodiments.

The polyamide elastomer of the present invention is obtainable byreaction of at least the components (a); (b); and (c), and (d) useddepending on the necessity. Examples of the method include a method ofsimultaneously mixing the components (a) to (c), or simultaneouslymixing the components (a) to (d) to cause reaction; and a method ofallowing the component (a) to react with the component (b), and thenadding the other components thereto to cause further reaction. From theviewpoint of efficiently synthesizing a block copolymer that has adesired hard segment and a desired soft segment, it is preferable toselect, among these methods, a method that has step (i) of mixing thecomponents (a) and (b) to cause reaction to obtain a prepolymer(hereinafter, called “step (i)”); and a step of mixing the prepolymerobtained in step (i) and the component (c) or the components (c) and (d)to cause reaction (hereinafter, called “step (ii)”).

The ratio between the components (a) and (b) mixed in step (i) is notparticularly limited. In order to easily obtain a hard segment with adesired length, it is preferable that the molar ratio (AB) of aminogroups in the component (a) (represented by (A)) to monocarboxyl groupsin the component (b) (represented by (B)) be 1/2 or higher and 5/4 orlower, more preferably and substantially be 1/1.

In either of the method involving simultaneous mixing of the component(a) to (c) or the components (a) to (d) or the method having steps (i)and (ii), it is preferable that the total number of moles of aminogroups in the component (a) to the component (c) or the components (a)to (d) be substantially the same as the number of moles of carboxylgroups in these components.

When using a compound that potentially disturbs the equimolar balancebetween the amino groups and the carboxyl groups in the method ofproducing a polyamide elastomer of the present invention, it isdesirable that the amount of the compound be low enough not to impairdesired physical properties.

The ratio between the components (a) to (c) mixed in the method ofproducing a polyamide elastomer of the present invention is notparticularly limited. It is preferable that the ratio of the component(a) to the total of the components (a) to (c) range from 70 to 98.5weight %, more preferably from 85 to 98 weight %; it is preferable thatthe ratio of the component (b) to the total of the components (a) to (c)range from 0.5 to 20 weight %, more preferably from 1 to 10 weight %; itis preferable that the ratio of the component (c) to the total of thecomponents (a) to (c) range from 0.5 to 20 weight %, more preferablyfrom 1 to 10 weight %. When the component (d) is used, the ratio betweenthe components (a) to (d) mixed is not particularly limited but it ispreferable that the ratio of the component (a) to the total of thecomponents (a) to (d) range from 70 to 98.5 weight %, more preferablyfrom 85 to 98 weight %; it is preferable that the ratio of the component(b) to the total of the components (a) to (d) range from 0.5 to 20weight %, more preferably from 1 to 10 weight %; it is preferable thatthe ratio of the component (c) to the total of the components (a) to (d)range from 0.5 to 20 weight %, more preferably from 1 to 10 weight %;and it is preferable that the ratio of the component (d) to the total ofthe components (a) to (d) range from 0.5 to 30 weight %, more preferablyfrom 1 to 20 weight %.

Accordingly, it is preferable to take step (ii) into consideration whendetermining the amounts of the components (a) and (b) to be mixed instep (i). In addition, it is preferable to take into consideration themolar ratio of amino groups to carboxyl groups contained in the total ofthe components (a) to (c) or the components (a) to (d), and it ispreferable to determine the amounts of the components so that asubstantial equimolar balance is successfully established between them,as described above. When the component (a) is a condensationpolymerization product, the amounts of the components to be mixed may bedetermined based on the compounds to be subjected to the condensationpolymerization.

The reactions in the steps (i) and (ii) in the method of producing apolyamide elastomer of the present invention may be carried out eitherin solvent or without solvent (namely, non-solvent reactions). For thepurpose of easily obtaining a desired polyamide elastomer withoutpurification or the like, it is preferable that the reactions be carriedout without solvent (namely, non-solvent reactions). Such non-solventreactions may be carried out by a melt kneading method. Therefore, it ispreferable that the reaction of the components (a) and (b) in step (i)and the reaction of the prepolymer and the component (c) or the reactionof the prepolymer and the components (c) and (d) in step (ii) be carriedout by a melt kneading method.

The polymerization reaction of the components (a) to (c) or thecomponents (a) to (d) in the method of producing a polyamide elastomerof the present invention may be normal-pressure melt polycondensationreaction, vacuum melt polycondensation reaction, or a combination ofthese. When the vacuum melt polycondensation is adopted, it ispreferable to set a pressure inside the reaction vessel from 0.1 to 0.01MPa in a nitrogen gas atmosphere, from the viewpoint of polymerizationreactivity. Any of the melt polycondensation reactions described abovemay be carried out by a melt kneading method without solvent.

The reaction temperature in the steps (i) and (ii) in the method ofproducing a polyamide elastomer of the present invention is notparticularly limited, as long as the polymerization reaction occurs.From the viewpoint of the balance between the reaction rate and thermalcracking inhibition, it is preferable that the reaction temperaturerange from 160 to 300° C., more preferably from 200 to 280° C. Thereaction temperature in the step (i) may be the same as or differentfrom the reaction temperature in the step (ii).

For the purpose of attaining a high molecular weight and inhibitingcoloration, for example, it is preferable that the polymerizationreaction time in the steps (i) and (ii) in the method of producing apolyamide elastomer of the present invention range from 3 to 10 hours.The polymerization reaction time in the step (i) may be the same as ordifferent from the polymerization reaction time in the step (ii).

The method of producing a polyamide elastomer of the present inventionmay be carried out either in a batch mode or in a continuous mode. Forexample, any of the following may be adopted: a batch mode that iscarried out in a batch-mode reaction tank or the like; and a continuousmode that is carried out in a single-tank or multi-tank continuousreaction apparatus, a tubular-shape continuous reaction apparatus, or acombination of these apparatuses.

In the production of the polyamide elastomer of the present invention, aphosphorus compound may be used as a catalyst, as needed. Examples ofthe phosphorus compound include phosphoric acid, pyrophosphoric acid,polyphosphoric acid, phosphorous acid, hypophosphorous acid, and alkalimetal salts and alkaline-earth metal salts thereof. Among these, aninorganic phosphorus compound such as phosphorous acid, hypophosphorousacid, and alkali metal salts and alkaline-earth metal salts thereof ispreferable from the viewpoints of enhancing polymerization reactionstability, imparting thermal stability to the resulting polyamideelastomer, and enhancing the dynamical properties of the resultingmolded article.

It is preferable that the amount (in terms of weight) of the phosphoruscompound added in at least one of steps (i) and (ii) be 10 ppm or higherand 10000 ppm or lower, more preferably 100 ppm or higher and 5000 ppmor lower relative to the total weight of the components (a) to (c) orthe total weight of the components (a) to (d) when the component (d) isused. At this time, if the component (a) is a condensationpolymerization product, the amount of the phosphorus compound added maybe determined based on the compounds to be subjected to the condensationpolymerization. The weight of the phosphorus compound added may not benecessarily equivalent to the content of the element phosphorus in theresulting polyamide elastomer, since a partial amount of the phosphoruscompound may be sometimes released from the reaction system in a form ofa reaction by-product. It is preferable that the content of the elementphosphorus in the resulting polyamide elastomer be 5 ppm or higher and5000 ppm or lower, more preferably 20 ppm or higher and 4000 ppm orlower, further preferably 30 ppm or higher and 3000 ppm or lower.

After the reaction of the components in the step (ii) is completed, astring of the resulting molten polymer may be, for example, pulled outof the reaction system, cooled, and made into pellets or the like asneeded.

The polyamide elastomer of the present invention contains appropriateamounts of polyether chain groups and polyamide groups. As a result, thepolyamide elastomer of the present invention does not greatly change itsphysical properties when it absorbs water. In addition, the polyamideelastomer of the present invention has excellent extrusion moldabilityand excellent roll moldability resulting from the melt properties of theresin, excellent blow moldability, and excellent strength and toughness.Thus, the polyamide elastomer of the present invention may be usable forproducing molded articles for use in various fields. For example, thepolyamide elastomer of the present invention may be subjected toextrusion molding to produce a member such as a tube, a hose, and amedical tube, or the polyamide elastomer of the present invention may besubjected to blow molding to produce a bottle, a container, a catheterballoon, and so on.

The polyamide elastomer of the present invention is particularlysuitable for use to produce a medical member used in a medical device.Examples of the medical member include catheter balloons and medicaltubes.

Next, the medical member made by using the polyamide elastomer isdescribed referring to the case in which the medical member is acatheter balloon. The scope of the present invention is, however, notlimited to this case.

A catheter balloon (hereinafter, simply called “balloon”) may beproduced by making a tube (hereinafter, it may be called “parison”)using the polyamide elastomer of the present invention and thensubjecting the resulting parison to further processing.

The method of making a parison using the polyamide elastomer may be atypical, known molding method. Examples of the method include extrusionmolding, injection molding, and melt spinning molding. The resultingparison is typically a cylinder with a uniform diameter in a long-axisdirection.

The method of producing a balloon from the parison may be a typical,known molding method. For example, a blow molding method such as freeblowing or mold blowing or a vacuum molding method may be employed tocarry out biaxial stretching to prepare a balloon with a desired shape.The temperature during molding is typically from 95 to 165° C.

It is preferable that the rate of enlargement of the inner diameter ofthe parison when formed into a balloon be 400% or greater and 900% orsmaller, more preferably 500% or greater and 800% or smaller. The rateof enlargement of the inner diameter in the present invention iscalculated by the following expression.Rate of enlargement of inner diameter (%)=((inner diameter of balloonwhen inflated during molding)/(inner diameter of parison))×100

The balloon produced in this way is subjected to examinations such asvisual examination, and only after it has passed the examinations, theballoon is eligible to be used as a medical member for use in a medicaldevice such as a balloon catheter. When the visual examination finds arhombic mark, a fish eye, or a crack on the surface, the balloon isevaluated as defective.

As described above, the polyamide elastomer of the present invention isexcellent at least in dynamical properties such as elasticity,elongation at break, and strength at break and also in workability suchas extrusion moldability in a molten state and blow moldability in asolid state. Therefore, the polyamide elastomer of the present inventionmay be used in various applications, such as medical device members;packaging materials for food and the like; members of electricaldevices, machines, and precision instruments; and automobile members.

EXAMPLES

(Measurement of Melt Flow Rate)

A melt flow rate (MFR) was measured with a G-01 melt indexer(manufactured by Toyo Seiki Seisaku-sho, Ltd.) in accordance withASTM-D3418. The resin sample was dried in an oven at 80° C. for 4 hoursfor the measurement.

(Measurement of Number Average Molecular Weight (Mn))

A number average molecular weight (Mn) was measured by gel permeationchromatography (GPC). The measurement by GPC was carried out using, as aGPC apparatus, a GPC unit manufactured by Shimadzu Corporation (anSCL-10Avp system controller, an LC-10ADvp pump, a CTO-10Avp column oven,and an RID-10A detector), an LF-404 column manufactured by SHODEX, andhexafluoroisopropanol as solvent. The molecular weight distribution thusobtained was used in combination with a calibration curve generated withthe use of a reference standard (polymethyl methacrylate, PMMA) todetermine the number average molecular weight in terms of PMMA.

The number average molecular weight thus measured varied about 10% and,therefore, the average value of two or three measurements was used.

(Tensile Test)

A tensile test was carried out using a specimen that was compliant withASTM-D638 (TYPES). The specimen was prepared in the following way: apellet of a polyamide elastomer obtained in an example or a comparativeexample was pressed with a Mini Test Press (manufactured by Toyo SeikiSeisaku-sho, Ltd.; trade name, MP-2FH) at 190° C., and then cooled; theresulting film with a thickness of 1 mm was subjected to die cuttingwith a die blade that was compliant with the above specification; andthe resultant was dried at 80° C. for 4 hours. The tensile test wascarried out at a rate of 200 mm/min.

(Measurement of Shore (D) Hardness)

A sheet with a thickness of 6 mm was subjected to Shore (D) measurementin accordance with ASTM-D2240 in a thermostatic chamber controlled at23° C. The sheet with a thickness of 6 mm was prepared from a pellet ofa polyamide elastomer obtained in an example or a comparative examplewith the same press machine as above. The measurement was carried outwith a load tester for D type durometer manufactured by Kobunshi KeikiCo., Ltd.

(Quantitative Assessment of Remaining Element Phosphorus)

Each of polyamide elastomers obtained in Examples 10 and 11 wassubjected to quantitative assessment of the element phosphorus containedtherein.

Pretreatment was carried out in the following way: about 0.1 g of asample was accurately weighed in a digestion vessel; thereto, sulfuricacid and nitric acid were added; and the resulting mixture was subjectedto high-pressure acidolysis with the use of a microwave digestion system(manufactured by Milestone General K.K.; trade name, ETHOS One). Theliquid obtained after digestion was diluted to 50 ml, which wassubjected to quantitative assessment. The quantitative assessment wascarried out by inductively coupled plasma (ICP) emissionspectrophotometry (with an ICPS-8100 device manufactured by ShimadzuCorporation).

(Visual Examination of Formed Balloon)

A parison molded in an example was subjected to blow molding to obtain aballoon. The resulting balloon was visually examined on the surface witha 20-power loupe for any cracks with a size of 0.0005 mm² or greater.

(Measurement of Compressive Strength)

A pellet of a polyamide elastomer obtained in an example or acomparative example was made into a blow molded article. The resultingblow molded article was heat sealed on one side, followed by measurementwith a burst leak tester (manufactured by Crescent Design, Inc.; tradename, MODEL 1000) in a water bath at 37° C.

Example 1

To a 3-L reaction vessel equipped with a stirrer, a temperaturecontroller, a pressure gauge, a nitrogen gas inlet, and a condensationwater outlet, 1200 g of 12-aminododecanoic acid and 0.6 g ofhypophosphorous acid were fed. The interior of the reaction vessel wassufficiently replaced with nitrogen. The temperature was raised to andkept at 280° C. for 1 hour for melting. Then, polymerization was allowedto proceed until the number average molecular weight reached 4100. Thus,a component (a) was obtained, which was to be used as a hard segment.

To the resultant, 43.8 g (0.30 mol) of adipic acid as a component (b)was added the amount of which was equivalent to the number of moles ofthe terminal amine groups contained in the hard segment. Reaction wasallowed to proceed at 220° C. for 1 hour for dicarboxylation of the hardsegment (step (i)).

Thereto, 180 g (0.300 mol) of a polyether diamine (Jeffamine ED600manufactured by Huntsman; having a value of (x+z) in formula (4) of 1 orgreater and 3.8 or smaller and a value of y in the same formula of 1 orgreater and 9.2 or smaller; and having a number average molecular weightranging from 500 to 700) as a component (c1) were added, so as to havethe total amount equivalent to the total number of moles of the terminalcarboxyl groups present on both ends of the dicarboxylated hard segmentobtained above. The temperature was raised to reach 260° C., at whichpolymerization was allowed to proceed for 5 hours to obtain a polymer(step (ii)).

After the completion of the polymerization, stirring was stopped andthen a string of colorless transparent polymer in a molten state waspulled out through a discharge port. The resulting string was cooledwith water and pelletized to obtain about 1 kg of pellets. The resultingpellets were subjected to measurement of MFR and the number averagemolecular weight (Mn). The results are shown in Table 2.

The pellets were made into a formed article (specimen), which wassubjected to a tensile test and also to measurement of Shore (D)hardness. The results are shown in Table 5.

Example 2

To a 3-L reaction vessel equipped with a stirrer, a temperaturecontroller, a pressure gauge, a nitrogen gas inlet, and a condensationwater outlet, 1200 g of 12-aminododecanoic acid and 0.6 g ofhypophosphorous acid were fed. The interior of the reaction vessel wassufficiently replaced with nitrogen. The temperature was raised to andkept at 280° C. for 1 hour for melting. Then, polymerization was allowedto proceed until the number average molecular weight reached 6800. Thus,a component (a) was obtained, which was to be used as a hard segment.

To the resultant, 25 g (0.17 mol) of adipic acid as a component (b) wasadded the amount of which was equivalent to the number of moles of theterminal amine groups contained in the hard segment. Reaction wasallowed to proceed at 220° C. for 1 hour for dicarboxylation of the hardsegment (step (i)).

Thereto, 103 g (0.172 mol) of a polyether diamine (Jeffamine ED600manufactured by Huntsman) as a component (c1) was added, the amount ofwhich was equivalent to the total number of moles of the terminalcarboxyl groups present on both ends of the dicarboxylated hard segmentobtained above. The temperature was raised to reach 260° C., at whichpolymerization was allowed to proceed for 5 hours to obtain a polymer(step (ii)).

After the completion of the polymerization, stirring was stopped andthen a string of colorless transparent polymer in a molten state waspulled out through a discharge port. The resulting string was cooledwith water and pelletized to obtain about 1 kg of pellets. The resultingpellets were subjected to measurement of MFR and the number averagemolecular weight (Mn). The results are shown in Table 2.

The pellets were made into a formed article (specimen), which wassubjected to a tensile test and also to measurement of Shore (D)hardness. The results are shown in Table 2.

Example 3

To a 3-L reaction vessel equipped with a stirrer, a temperaturecontroller, a pressure gauge, a nitrogen gas inlet, and a condensationwater outlet, 1200 g of 12-aminododecanoic acid and 0.6 g ofhypophosphorous acid were fed. The interior of the reaction vessel wassufficiently replaced with nitrogen. The temperature was raised to andkept at 280° C. for 1 hour for melting. Then, polymerization was allowedto proceed until the number average molecular weight reached 9900. Thus,a component (a) was obtained, which was to be used as a hard segment.

To the resultant, 17.5 g (0.12 mol) of adipic acid as a component (b)was added the amount of which was equivalent to the number of moles ofthe terminal amine groups contained in the hard segment. Reaction wasallowed to proceed at 220° C. for 1 hour for dicarboxylation of the hardsegment (step (i)).

Thereto, 72 g (0.117 mol) of a polyether diamine (Jeffamine ED600manufactured by Huntsman) as a component (c1) was added, the amount ofwhich was equivalent to the total number of moles of the terminalcarboxyl groups present on both ends of the dicarboxylated hard segmentobtained above. The temperature was raised to reach 260° C., at whichpolymerization was allowed to proceed for 4 hours to obtain a polymer(step (ii)).

After the completion of the polymerization, stirring was stopped andthen a string of colorless transparent polymer in a molten state waspulled out through a discharge port. The resulting string was cooledwith water and pelletized to obtain about 1 kg of pellets. The resultingpellets were subjected to measurement of MFR and the number averagemolecular weight (Mn). The results are shown in Table 2.

The pellets were made into a formed article (specimen), which wassubjected to a tensile test and also to measurement of Shore (D)hardness. The results are shown in Table 2.

Example 4

To a 3-L reaction vessel equipped with a stirrer, a temperaturecontroller, a pressure gauge, a nitrogen gas inlet, and a condensationwater outlet, 1200 g of 12-aminododecanoic acid and 0.6 g ofhypophosphorous acid were fed. The interior of the reaction vessel wassufficiently replaced with nitrogen. The temperature was raised to andkept at 280° C. for 1 hour for melting. Then, polymerization was allowedto proceed until the number average molecular weight reached 5000. Thus,a component (a) was obtained, which was to be used as a hard segment.

To the resultant, 35 g (0.24 mol) of adipic acid as a component (b) wasadded the amount of which was equivalent to the number of moles of theterminal amine groups contained in the hard segment. Reaction wasallowed to proceed at 220° C. for 1 hour for dicarboxylation of the hardsegment (step (i)).

Thereto, 22.3 g (0.19 mol) of hexamethylenediamine as a component (d)and 28.8 g (0.048 mol) of a polyether diamine (Jeffamine ED600manufactured by Huntsman) as a component (c1) were added, so as to havethe total amount equivalent to the total number of moles of the terminalcarboxyl groups present on both ends of the dicarboxylated hard segmentobtained above. The temperature was raised to reach 260° C., at whichpolymerization was allowed to proceed for 4 hours to obtain a polymer(step (ii)).

After the completion of the polymerization, stirring was stopped andthen a string of colorless transparent polymer in a molten state waspulled out through a discharge port. The resulting string was cooledwith water and pelletized to obtain about 1 kg of pellets. The resultingpellets were subjected to measurement of MFR and the number averagemolecular weight (Mn). The results are shown in Table 2.

The pellets were made into a formed article (specimen), which wassubjected to a tensile test and also to measurement of Shore (D)hardness. The results are shown in Table 2.

Example 5

To a 3-L reaction vessel equipped with a stirrer, a temperaturecontroller, a pressure gauge, a nitrogen gas inlet, and a condensationwater outlet, 1200 g of 12-aminododecanoic acid and 0.6 g ofhypophosphorous acid were fed. The interior of the reaction vessel wassufficiently replaced with nitrogen. The temperature was raised to andkept at 280° C. for 1 hour for melting. Then, polymerization was allowedto proceed until the number average molecular weight reached 5200. Thus,a component (a) was obtained, which was to be used as a hard segment.

To the resultant, 35 g (0.24 mol) of adipic acid as a component (b) wasadded the amount of which was equivalent to the number of moles of theterminal amine groups contained in the hard segment. Reaction wasallowed to proceed at 220° C. for 1 hour for dicarboxylation of the hardsegment (step (i)).

Thereto, 19.5 g (0.17 mol) of hexamethylenediamine as a component (d)and 43.2 g (0.072 mol) of a polyether diamine (Jeffamine ED600manufactured by Huntsman) as a component (c1) were added, so as to havethe total amount equivalent to the total number of moles of the terminalcarboxyl groups present on both ends of the dicarboxylated hard segmentobtained above. The temperature was raised to reach 260° C., at whichpolymerization was allowed to proceed for 4 hours to obtain a polymer(step (ii)).

After the completion of the polymerization, stirring was stopped andthen a string of colorless transparent polymer in a molten state waspulled out through a discharge port. The resulting string was cooledwith water and pelletized to obtain about 1 kg of pellets. The resultingpellets were subjected to measurement of MFR and the number averagemolecular weight (Mn). The results are shown in Table 2.

The pellets were made into a formed article (specimen), which wassubjected to a tensile test and also to measurement of Shore (D)hardness. The results are shown in Table 2.

Example 6

To a 3-L reaction vessel equipped with a stirrer, a temperaturecontroller, a pressure gauge, a nitrogen gas inlet, and a condensationwater outlet, 1200 g of 12-aminododecanoic acid and 0.6 g ofhypophosphorous acid were fed. The interior of the reaction vessel wassufficiently replaced with nitrogen. The temperature was raised to andkept at 280° C. for 1 hour for melting. Then, polymerization was allowedto proceed until the number average molecular weight reached 5400. Thus,a component (a) was obtained, which was to be used as a hard segment.

To the resultant, 35 g (0.24 mol) of adipic acid as a component (b) wasadded the amount of which was equivalent to the number of moles of theterminal amine groups contained in the hard segment. Reaction wasallowed to proceed at 220° C. for 1 hour for dicarboxylation of the hardsegment (step (i)).

Thereto, 14 g (0.12 mol) of hexamethylenediamine as a component (d) and72 g (0.12 mol) of a polyether diamine (Jeffamine ED600 manufactured byHuntsman) as a component (c1) were added, so as to have the total amountequivalent to the total number of moles of the terminal carboxyl groupspresent on both ends of the dicarboxylated hard segment obtained above.The temperature was raised to reach 260° C., at which polymerization wasallowed to proceed for 4 hours to obtain a polymer (step (ii)).

After the completion of the polymerization, stirring was stopped andthen a string of colorless transparent polymer in a molten state waspulled out through a discharge port. The resulting string was cooledwith water and pelletized to obtain about 1 kg of pellets. The resultingpellets were subjected to measurement of MFR and the number averagemolecular weight (Mn). The results are shown in Table 2.

The pellets were made into a formed article (specimen), which wassubjected to a tensile test and also to measurement of Shore (D)hardness. The results are shown in Table 2.

Example 7

To a 3-L reaction vessel equipped with a stirrer, a temperaturecontroller, a pressure gauge, a nitrogen gas inlet, and a condensationwater outlet, 1200 g of 12-aminododecanoic acid and 0.6 g ofhypophosphorous acid were fed. The interior of the reaction vessel wassufficiently replaced with nitrogen. The temperature was raised to andkept at 280° C. for 1 hour for melting. Then, polymerization was allowedto proceed until the number average molecular weight reached 5100. Thus,a component (a) was obtained, which was to be used as a hard segment.

To the resultant, 35 g (0.24 mol) of adipic acid as a component (b) wasadded the amount of which was equivalent to the number of moles of theterminal amine groups contained in the hard segment. Reaction wasallowed to proceed at 220° C. for 1 hour for dicarboxylation of the hardsegment (step (i)).

Thereto, 8 g (0.069 mol) of hexamethylenediamine as component (d) and101 g (0.168 mol) of a polyether diamine (Jeffamine ED600 manufacturedby Huntsman) as a component (c1) were added, so as to have the totalamount equivalent to the total number of moles of the terminal carboxylgroups present on both ends of the dicarboxylated hard segment obtainedabove. The temperature was raised to reach 260° C., at whichpolymerization was allowed to proceed for 5 hours to obtain a polymer(step (ii)).

After the completion of the polymerization, stirring was stopped andthen a string of colorless transparent polymer in a molten state waspulled out through a discharge port. The resulting string was cooledwith water and pelletized to obtain about 1 kg of pellets. The resultingpellets were subjected to measurement of MFR and the number averagemolecular weight (Mn). The results are shown in Table 2.

The pellets were made into a formed article (specimen), which wassubjected to a tensile test and also to measurement of Shore (D)hardness. The results are shown in Table 2.

Example 8

To a 3-L reaction vessel equipped with a stirrer, a temperaturecontroller, a pressure gauge, a nitrogen gas inlet, and a condensationwater outlet, 1200 g of 12-aminododecanoic acid and 0.6 g ofhypophosphorous acid were fed. The interior of the reaction vessel wassufficiently replaced with nitrogen. The temperature was raised to andkept at 280° C. for 1 hour for melting. Then, polymerization was allowedto proceed until the number average molecular weight reached 4900. Thus,a component (a) was obtained, which was to be used as a hard segment.

To the resultant, 35 g (0.24 mol) of adipic acid as a component (b) wasadded the amount of which was equivalent to the number of moles of theterminal amine groups contained in the hard segment. Reaction wasallowed to proceed at 220° C. for 1 hour for dicarboxylation of the hardsegment (step (i)).

Thereto, 3 g (0.026 mol) of hexamethylenediamine as a component (d) and130 g (0.217 mol) of a polyether diamine (Jeffamine ED600 manufacturedby Huntsman) as a component (c1) were added, so as to have the totalamount equivalent to the total number of moles of the terminal carboxylgroups present on both ends of the dicarboxylated hard segment obtainedabove. The temperature was raised to reach 260° C., at whichpolymerization was allowed to proceed for 4 hours. Then, the pressurewas reduced, at which polymerization was allowed to continue for another4 hours. Thus, a polymer was obtained (step (ii)).

After the completion of the polymerization, stirring was stopped andthen a string of colorless transparent polymer in a molten state waspulled out through a discharge port. The resulting string was cooledwith water and pelletized to obtain about 1 kg of pellets. The resultingpellets were subjected to measurement of MFR and the number averagemolecular weight (Mn). The results are shown in Table 2.

The pellets were made into a formed article (specimen), which wassubjected to a tensile test and also to measurement of Shore (D)hardness. The results are shown in Table 2.

Example 9

To a 3-L reaction vessel equipped with a stirrer, a temperaturecontroller, a pressure gauge, a nitrogen gas inlet, and a condensationwater outlet, 1200 g of 12-aminododecanoic acid and 0.6 g ofhypophosphorous acid were fed. The interior of the reaction vessel wassufficiently replaced with nitrogen. The temperature was raised to andkept at 280° C. for 1 hour for melting. Then, polymerization was allowedto proceed until the number average molecular weight reached 5100. Thus,a component (a) was obtained, which was to be used as a hard segment.

To the resultant, 48.5 g (0.24 mol) of sebacic acid as a component (b)was added the amount of which was equivalent to the number of moles ofthe terminal amine groups contained in the hard segment. Reaction wasallowed to proceed at 220° C. for 1 hour for dicarboxylation of the hardsegment (step (i)).

Thereto, 24 g (0.12 mol) of dodecamethylenediamine as a component (d)and 72 g (0.12 mol) of a polyether diamine (Jeffamine ED600 manufacturedby Huntsman) as a component (c1) were added, so as to have the totalamount equivalent to the total number of moles of the terminal carboxylgroups present on both ends of the dicarboxylated hard segment obtainedabove. The temperature was raised to reach 260° C., at whichpolymerization was allowed to proceed for 4 hours to obtain a polymer(step (ii)).

After the completion of the polymerization, stirring was stopped andthen a string of colorless transparent polymer in a molten state waspulled out through a discharge port. The resulting string was cooledwith water and pelletized to obtain about 1 kg of pellets. The resultingpellets were subjected to measurement of MFR and the number averagemolecular weight (Mn). The results are shown in Table 2.

The pellets were made into a formed article (specimen), which wassubjected to a tensile test and also to measurement of Shore (D)hardness. The results are shown in Table 2.

Comparative Example 1

To a 3-L reaction vessel equipped with a stirrer, a temperaturecontroller, a pressure gauge, a nitrogen gas inlet, and a condensationwater outlet, 1200 g of 12-aminododecanoic acid and 0.6 g ofhypophosphorous acid were fed. The interior of the reaction vessel wassufficiently replaced with nitrogen. The temperature was raised to andkept at 280° C. for 1 hour for melting. Then, polymerization was allowedto proceed until the number average molecular weight reached 2800. Thus,a compound was obtained, which was to be used as a hard segment. GPCevaluation was carried out, which observed peaks attributable to amonomer and a dimer.

To the resultant, 58 g (0.40 mol) of adipic acid was added the amount ofwhich was equivalent to the number of moles of the terminal amine groupscontained in the hard segment. Reaction was allowed to proceed at 220°C. for 1 hour for dicarboxylation of the hard segment.

Thereto, 240 g (0.40 mol) of a polyether diamine (Jeffamine ED600manufactured by Huntsman) was added, the amount of which was equivalentto the total number of moles of the terminal carboxyl groups present onboth ends of the dicarboxylated hard segment obtained above. Thetemperature was raised to reach 260° C., at which polymerization wasallowed to proceed for 3 hours. When 3 hours had passed, the meltviscosity stopped increasing. So as to terminate polymerization,stirring was stopped. Thus, a polymer was obtained. A string ofcolorless transparent polymer in a molten state was pulled out through adischarge port. The resulting string was cooled with water andpelletized to obtain about 1 kg of pellets. The resulting pellets weresubjected to measurement of MFR and the number average molecular weight(Mn). The results are shown in Table 2.

The pellets were made into a formed article (specimen), which wassubjected to a tensile test and also to measurement of Shore (D)hardness. The results are shown in Table 2.

Comparative Example 2

To a 3-L reaction vessel equipped with a stirrer, a temperaturecontroller, a pressure gauge, a nitrogen gas inlet, and a condensationwater outlet, 1200 g of 12-aminododecanoic acid and 0.6 g ofhypophosphorous acid were fed. The interior of the reaction vessel wassufficiently replaced with nitrogen. The temperature was raised to andkept at 280° C. for 1 hour for melting. Then, polymerization was allowedto proceed until the number average molecular weight reached 12500.Thus, a compound was obtained, which was to be used as a hard segment.

To the resultant, 14.6 g (0.10 mol) of adipic acid was added the amountof which was equivalent to the number of moles of the terminal aminegroups contained in the hard segment. Reaction was allowed to proceed at220° C. for 1 hour for dicarboxylation of the hard segment.

Thereto, 60 g (0.100 mol) of a polyether diamine (Jeffamine ED600manufactured by Huntsman) was added, so as to have the amount equivalentto the total number of moles of the terminal carboxyl groups present onboth ends of the dicarboxylated hard segment obtained above. Thetemperature was raised to reach 260° C., at which polymerization wasallowed to proceed for 4 hours. Thus, a polymer was obtained.

After the completion of the polymerization, stirring was stopped andthen a string of colorless transparent polymer in a molten state waspulled out through a discharge port. The resulting string was cooledwith water and pelletized to obtain about 1 kg of pellets. The resultingpellets were subjected to measurement of MFR and the number averagemolecular weight (Mn). The results are shown in Table 2.

The pellets were made into a formed article (specimen), which wassubjected to a tensile test and also to measurement of Shore (D)hardness. The results are shown in Table 2.

Comparative Example 3

To a 3-L reaction vessel equipped with a stirrer, a temperaturecontroller, a pressure gauge, a nitrogen gas inlet, and a condensationwater outlet, 1200 g of 12-aminododecanoic acid and 0.6 g ofhypophosphorous acid were fed. The interior of the reaction vessel wassufficiently replaced with nitrogen. The temperature was raised to andkept at 280° C. for 1 hour for melting. After the entire content of thevessel had melted, the temperature was decreased to 260° C., at whichpolymerization was allowed to proceed for 4 hours to obtain a polymer.

After the completion of the polymerization, stirring was stopped andthen a string of colorless transparent polymer in a molten state waspulled out through a discharge port. The resulting string was cooledwith water and pelletized to obtain about 1 kg of pellets. The resultingpellets were subjected to measurement of MFR and the number averagemolecular weight (Mn). The results are shown in Table 2.

The pellets were made into a formed article, which was subjected to atensile test and also to measurement of Shore (D) hardness. The resultsare shown in Table 2.

Comparative Example 4

To a 3-L reaction vessel equipped with a stirrer, a temperaturecontroller, a pressure gauge, a nitrogen gas inlet, and a condensationwater outlet, 1200 g of 6-aminohexanoic acid and 0.6 g ofhypophosphorous acid were fed. To the resulting mixture, the followingwere added: 35 g (0.24 mol) of adipic acid the amount of which wasequivalent to the number of moles of the terminal amine groups presenton one end of the resulting hard segment that was assumed to have anumber average molecular weight of 5000; and 144 g (0.24 mol) of apolyether diamine (Jeffamine ED600 manufactured by Huntsman) the amountof which was equivalent to the total number of moles of the terminalcarboxyl groups present on both ends of the dicarboxylated hard segment.The interior of the reaction vessel was sufficiently replaced withnitrogen. The temperature was raised to and kept at 280° C. for 1 hourfor melting. Then, the temperature was decreased to 260° C., at whichpolymerization was allowed to proceed for 6 hours.

After the completion of the polymerization, stirring was stopped andthen a string of colorless transparent polymer in a molten state waspulled out through a discharge port. The resulting string was cooledwith water and pelletized to obtain about 1 kg of pellets. The resultingpellets were subjected to measurement of MFR and the number averagemolecular weight (Mn). The results are shown in Table 2.

The pellets were made into a formed article (specimen), which wassubjected to a tensile test and also to measurement of Shore (D)hardness. The results are shown in Table 2.

TABLE 2 Elongation Strength MFR Shore (D) at break at break (g/10 min)Mn hardness (%) (MPa) Example 1 15.1 84000 66 420 73 Example 2 14.058000 68 404 74 Example 3 12.0 41000 70 380 74 Example 4 5.0 43226 73358 70 Example 5 6.2 47811 72 360 68 Example 6 11.9 45166 70 375 73Example 7 13.1 70862 67 410 68 Example 8 14.3 78950 66 430 72 Example 912.0 56980 67 406 77 Comparative 30.1 45000 65 346 55 Example 1Comparative 8.9 23000 72 282 61 Example 2 Comparative 3.2 18000 74 25664 Example 3 Comparative 17.0 71000 63 279 65 Example 4

Each of the polyamide elastomers obtained in Examples 1 to 9 had an MFRvalue suitable for extrusion molding; was excellent in melt moldability;and was excellent in mechanical properties, such as elongation at breakand strength at break, as proven by the tensile test. With theseproperties in such excellent balance, these polyamide elastomersobtained in the examples are suitable for use in production of medicaltubes and balloons. Comparison between the results of the examples andthose of the comparative examples has proven that the polyamideelastomers obtained in the examples are superior in elongation at breakand strength at break to those obtained in the comparative examples witha similar Shore (D) hardness.

Example 10

A transparent pellet was obtained in the same manner as in Example 3except that the amount of hypophosphorous acid was changed to 0.13 g(100 ppm). The resulting pellet was subjected to extrusion molding toobtain a tube (parison). The resulting parison was subjected to blowmolding to obtain a catheter balloon with a rate of enlargement of theinner diameter of 640%. Table 6 shows the concentration of the elementphosphorus, the result of molding procedure, and the result of thepressure resistance test for the molded article. The concentration (100ppm) of hypophosphorous acid when added was determined based on thetotal amount of 12-aminododecanoic acid, adipic acid,hexamethylenediamine, and polyether diamine. This manner of determiningthe concentration of hypophosphorous acid also applies to Example 11.

Example 11

A transparent pellet was obtained in the same manner as in Example 3except that the amount of hypophosphorous acid was changed to 1.32 g(1000 ppm). The resulting pellet was subjected to extrusion molding toobtain a tube (parison). The resulting parison was subjected to blowmolding to obtain a catheter balloon with a rate of enlargement of theinner diameter of 640%. Table 6 shows the concentration of the elementphosphorus, the result of molding procedure, and the result of thepressure resistance test for the molded article.

TABLE 3 Concentration of phosphorus Concentration of Rate of compoundwhen element phosphorus enlargement of Compressive added in pellet innerdiameter strength (ppm) (ppm) Cracks (%) (atm) Example 10 100 45 None640 22 Example 11 1000 450 None 640 21

As long as the concentration of the element phosphorus was within thecertain range, excellent moldability of a parison into a balloon wasobtained with no cracks even at a great rate of enlargement of the innerdiameter. This result indicates that the compressive strength has beenfurther enhanced.

The invention claimed is:
 1. A polyamide elastomer that is a reactionproduct of at least components (a), (b), and (c): the component (a)being at least one compound represented by formula (1):HOOC—R₁

NH—CO—R₁

_(n)NH₂  (1) where each R₁ independently represents a linear saturatedhydrocarbon group containing 1 or more carbon atoms; n represents a realnumber of 0 or greater; and when the formula contains two or more typesof repeating units each containing R₁, n represents a total number ofthe two or more types of the repeating units each containing R₁, thecomponent (a) having a number average molecular weight of 4000 or higherand 10,000 or lower; the component (b) being at least one compoundrepresented by formula (2):HOOC—R₂—COOH  (2) where R₂ represents a direct bond or a linearsaturated hydrocarbon group containing 1 or more carbon atoms; thecomponent (c) being at least one compound represented by formula (3):H₂N—R₄

O—R₄

_(m)NH₂  (3) where each R₄ independently represents a saturatedhydrocarbon group containing 1 or more carbon atoms; m represents a realnumber of 1 or greater; and when the formula contains two or more typesof repeating units each containing R₄, m represents a total number ofthe two or more types of the repeating units each containing R₄, thecomponent (c) having a number average molecular weight of 500 or higherand 700 or lower.
 2. The polyamide elastomer according to claim 1 thatis a reaction product of at least the components (a) to (c) and acomponent (d), the component (d) being at least one compound representedby formula (4):H₂N—R₃—NH₂  (4) where R₃ represents a saturated hydrocarbon groupcontaining 1 or more carbon atoms.
 3. The polyamide elastomer accordingto claim 1 or 2, wherein the component (c) is a component (c1), thecomponent (c1) being at least one compound represented by formula (5):

where (x+z) represents a real number of 1 or greater and 6 or smaller;and y represents a real number of 1 or greater and 20 or smaller.
 4. Thepolyamide elastomer according to claim 1, wherein the component (d) isat least one aliphatic diamine selected from ethylenediamine,trimethylenediamine, tetramethylenediamine, hexamethylenediamine,undecamethylenediamine, dodecamethylenediamine, and2,2-4/2,4,4-trimethylhexamethylenediamine.
 5. The polyamide elastomeraccording to claim 1, wherein a molar ratio (A/B) of amino groups in thecomponent (a) (represented by (A)) to monocarboxyl groups in thecomponent (b) (represented by (B)) is substantially 1/1.
 6. Thepolyamide elastomer according to claim 1, comprising a phosphoruscompound in a manner of containing element phosphorus in an amount of 5ppm or higher and 5000 ppm or lower.
 7. A medical device comprising amember that is made by using the polyamide elastomer according toclaim
 1. 8. The medical device according to claim 7, wherein the memberis a catheter balloon or a medical tube.
 9. A method of producing thepolyamide elastomer according to claim 1, the method comprising: step(i) of allowing the component (a) and the component (b) to react,thereby obtaining a prepolymer; and step (ii) of mixing the prepolymerwith the component (c) to react with each other.
 10. The method ofproducing the polyamide elastomer according to claim 9, wherein theprepolymer is mixed with the component (c) and the component (d) toreact with each other.
 11. The method of producing the polyamideelastomer according to claim 9 or 10, wherein each of the components inat least the steps (i) and (ii) is caused to react by a melt kneadingmethod.
 12. The method of producing the polyamide elastomer according toclaim 9 or 10, further comprising adding a phosphorus compound in atleast one of the steps (i) and (ii) in an amount of 10 ppm or higher and10000 ppm or lower relative to a total amount of the components (a) to(c) or a total amount of the component (a) to (d).